Classifications

• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B1/00—Optical elements characterised by the material of which they are made; Optical coatings for optical elements
  • G02B1/10—Optical coatings produced by application to, or surface treatment of, optical elements
  • G02B1/11—Anti-reflection coatings
  • G02B1/113—Anti-reflection coatings using inorganic layer materials only
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
  • H01L31/02—Details
  • H01L31/0216—Coatings
  • H01L31/02161—Coatings for devices characterised by at least one potential jump barrier or surface barrier
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
  • H01L31/02—Details
  • H01L31/0216—Coatings
  • H01L31/02161—Coatings for devices characterised by at least one potential jump barrier or surface barrier
  • H01L31/02167—Coatings for devices characterised by at least one potential jump barrier or surface barrier for solar cells
  • H01L31/02168—Coatings for devices characterised by at least one potential jump barrier or surface barrier for solar cells the coatings being antireflective or having enhancing optical properties for the solar cells
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
  • H01L33/02—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies
  • H01L33/20—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies with a particular shape, e.g. curved or truncated substrate
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B82—NANOTECHNOLOGY
  • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
  • B82Y20/00—Nanooptics, e.g. quantum optics or photonic crystals
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B82—NANOTECHNOLOGY
  • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
  • B82Y40/00—Manufacture or treatment of nanostructures
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B1/00—Optical elements characterised by the material of which they are made; Optical coatings for optical elements
  • G02B1/02—Optical elements characterised by the material of which they are made; Optical coatings for optical elements made of crystals, e.g. rock-salt, semi-conductors
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B2207/00—Coding scheme for general features or characteristics of optical elements and systems of subclass G02B, but not including elements and systems which would be classified in G02B6/00 and subgroups
  • G02B2207/101—Nanooptics
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L2933/00—Details relating to devices covered by the group H01L33/00 but not provided for in its subgroups
  • H01L2933/0083—Periodic patterns for optical field-shaping in or on the semiconductor body or semiconductor body package, e.g. photonic bandgap structures
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
  • H01L33/02—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies
  • H01L33/26—Materials of the light emitting region
  • H01L33/30—Materials of the light emitting region containing only elements of Group III and Group V of the Periodic Table
  • H01L33/32—Materials of the light emitting region containing only elements of Group III and Group V of the Periodic Table containing nitrogen

Definitions

• the invention relates to the fabrication of nano-patterned surfaces for application in optical and related device.
• Electromagnetic radiation here meaning UV light, visible light, near infrared light, mid infrared light and far infrared light, is reflected at the interface between two media due to abrupt changes in the speed of light as it passes from one media into the next.
• 'abrupt' means over a distance approximating the wavelength of light in the media. Since the speed of light is defined by the refractive index of the material in which it is travelling, optical reflections can equivalently be described as arising from abrupt changes in the refractive index of the media.
• Undesirable optical reflections can be mitigated by gradating the refractive index experienced by light as it travels from one media into the next. Practically this can be achieved by sub-wavelength texturing or patterning the substrate media. Texturing reduces the abruptness of the refractive index discontinuity experienced by light and thereby the optical reflectivity.
• the extensive benefits of the new generation of nanostructured surfaces is very promising for enhancing light absorption efficiency in optical or photonic devices.
• the low throughput and the high cost of available technologies such as interference lithography for fabrication of nanostructures has proved to be a difficult technological hurdle for advanced manufacturing.
• BCP block copolymer
• Nano patterning the surface of LEDs using block copolymers can improve the extraction efficiency.
• Nano-structures have been widely studied as photonic crystals, an antireflection structure, and nano-textures for higher luminescent LEDs.
• these structures are generally fabricated by electron beam lithography (EBL) and dry etching.
• EBL electron beam lithography
• dry etching There are two major problems with electron beam lithography method:
• etch contrast is the difference in etch rate between the resist used to create the structures and substrate being etched
• polymer resists and substrates such as GaN, InGaAIP, Sic and sapphire. It is, therefore extremely difficult (if not impossible) to pattern transfer the lithography masks to the substrate and fabricate tall arrays of nanopillars [Samsung 2009].
• Block copolymer (BCP) self- assembly is a solution-based process that offers an alternative route to produce highly ordered nanostructures.
• BCP Block copolymer
• BCP state of the art techniques is advancing the technology beyond 1 D and 2D photonic crystals in the range of visible light which is slow and difficult.
• the reason for this lies in the fact that for nanofeatures to modulate visible photons with wavelengths in the range 400- 700 nm, they must be greater than 100 nm (typically 1 ⁇ 4 wavelength).
• BCPs do not easily phase separate into their signature ordered pattern above 100 nm. This is due to the significant kinetic penalty arising from higher entanglement in high molecular weight polymers.
• SOA state-of-the-art
• a method of fabricating a nano-patterned surface for application in a photonic, optical or other related device comprising the steps of:
• BCP block copolymer
• phase separating the BCPs using at least one solvent selected to facilitate polymer chain mobilisation and lead to phase separation to fabricate said nano-patterned surface; wherein the nano-patterned surface comprises an ordered array of structures and having a domain or diameter of 100nm or greater.
• the phase separation step uses two or more solvents and the solvent ratio is selected to facilitate the chain mobilisation and lead to phase separation.
• the structure domain or diameter size is tuned by selecting the volume fraction of the block components.
• the method takes place in a sealed housing defining a volume and the solvent is selected based on said volume.
• the invention achieves phase separation in high molecular weight BCPs, forming well-ordered hexagonal cylinder patterns with feature size and periodicity of -1 15 and 180 nm respectively. Pattern transfer of such large features can be made for the first time.
• BCP Brunauer-Teller
• sub-wavelength structures on Si, glass, GaN, and germanium for enhanced broadband antireflection (AR) in photonic devices operating in the wavelength range from visible to near infrared (Vis-NIR) can be fabricated.
• a reduction in reflectivity by a factor of >100 achieved by overcoming the 100 nm size limit in block copolymers.
• a broadband antireflection less than 0.16% was observed, over the entire spectrum of 400-900 nm at angle of incidence (AOI) of 30°.
• the high molecular weight BCP comprises 440k-353k) g/mol, volume fraction of PS:P2VP 58:42.
• the step of depositing the block copolymer (BCP) material on the substrate material is performed by at least one of spin coating film; drop casting or dip coating.
• the step of texturing the height of the nano-patterned surface to a desired value is provided.
• the nano-pattern surface comprises an array of pillar or wire like structures and having a domain or diameter of approximately 100nm or greater.
• the nano-pattern surface comprises an array of substantially conical shaped structures and having a diameter of approximately 100nm or greater and a length of approximately 100nm or greater.
• the thickness of the BCP material is selected from a range of 100nm to 500nm.
• the substrate layer comprises at least one of: semiconductor material, silicon; gallium nitride; silicon carbide; glass; metal or plastic.
• the step of controlling the size and shape of the nano- pattern surface In one embodiment the step of controlling the size and shape of the nano- pattern surface.
• the step of incorporating metal oxide particles within the BCP material is a step of incorporating metal oxide particles within the BCP material.
• the step of direct etching through a metallised mask In one embodiment there is provided the step of transferring the nano-pattern to the substrate material to provide an antireflective surface with a low reflectivity in a wide range of wavelength.
• a subwavelength grating made from the same material as the substrate and the index matching at the substrate interfaces provides improved anti-reflecting performance.
• a photonic or optical device comprising a substrate material wherein a surface of the substrate material comprises an array of pillar or wire like structures and having a domain or diameter of approximately 100nm or greater.
• the substrate material and the array of pillar or wire like structures are the one material with no interface layer or boundary between the array and the substrate.
• a method of fabricating a nano- patterned surface for application in a photonic, optical or other related device comprising the steps of:
• BCP block copolymer
• a system for fabricating a nano- patterned surface for application in a photonic, optical or other related device comprising one or more modules adapted for:
• BCP block copolymer
• the invention provides fabrication of nano-patterned surfaces of > 100 nm feature size via block copolymer lithography for application in photonic and related device applications.
• the ordered sub-wavelength patterns will reduce reflections at the LED- air interface and thereby increase light output of the emitters.
• the highly ordered pattern will improve and control the direction of the emitted light.
• the invention greatly improves anti-reflection properties without using any coatings.
• the coating approach has numerous disadvantages but the primary ones here are: (1 ) they are invariably narrowband, and (2) they are vulnerable to damage at high optical powers.
• the invention is both broadband and will survive much higher optical power densities due to the absence of a coating (typically a dielectric material).
• the invention comprises the step direct etching through a metallised mask.
• the step of incorporating metal oxide particles within the polymer is provided.
• Light emitting materials such as gallium nitride and silicon carbide can be used as the substrate.
• the size and shape of the nanostructure can be customised by the molecular weight and volume fraction of the polymer blocks.
• pattern transferred the BCP mask to silicon substrate by reactive ion etch (ICP-RIE).
• the final product is black silicon, consists of hexagonally packed conic Si nano-features with diameter above 100nm and periodicity of 200 nm. The height of the Si nanopillars varies from 100 nm to higher than 1 micron.
• the subwavelength grating is made from the same material as the substrate (Si), the index matching at the substrate interfaces has led to much improved anti-reflecting performance.
• the reflectivity of the silicon substrate shows one order of magnitude reduction in a broad range of wavelength from NIR to UV-visible, below 1 %.
• the substrate material can be glass or sapphire. Glass and sapphire can be used for application in electronic device displays.
• the BCP process can be modified to achieve phase separation.
• the dimension of the features has to be modified to accommodate the higher refractive index of glass for modulation of light.
• the etch process can be implemented on glass and sapphire.
• Amorphous glass is a hard material and it is not easy to (plasma) etch.
• Most glass etch recipes are based on wet etch. However, for the application, we need to apply anisotropic etch to fabricate nanopillars.
• high-resolution, cost-effective patterning of curved surfaces is essential for many applications, such as microelectromechanical systems (MEMS), electronic devices, and optics.
• MEMS microelectromechanical systems
• soft nanoimprint lithography has been demonstrated as a high-throughput, low-cost lithographic technique, it still needs a soft mould (usually PDMS based) which will not stand the harsh etch environment to create tall glass nanopillars.
• Nanoimprint lithography usually cannot provide high aspect ratio (e.g. >2) nanopillars.
• the large BCP patterning technique according to the invention can be applied on curved surfaces without any need for the mould.
• Figure 2 illustrates a quantitative analysis of the feature size in Figure 1 ;
• the table provides the information regarding to the dimension of the areas analysed including defects and number of features in (a).
• Figure 3 illustrates domain size distribution for diameter (CD). Data was collected from 17 images of 10 individual samples. An example of the output detected features and Delaunay triangulation are also shown.
• Figure 4 illustrates the pitch size distribution is 180 ⁇ 18nm for 80% of the spacing in Figure 1 .
• Figure 5 illustrates SEM images of Si nanopillars fabricated by large molecular weight block copolymers. Top row, Top down images with different etch time. Bottom row, the cross section image of the pillars with different height (d) 100 nm, (e) 485 nm and (f) 600 nm
• Figure 6 illustrates optical characterisations of nanostructured Si samples. Broadband omnidirectional antireflection properties of silicon nanopillars by block copolymer self-assembly 30-75 5 .
• Figure 7 illustrates angular dependence of SiNPs with various height at different angle of incidence: (g) 45°, (h) 60°, (i) 70° and (j) 75°. Note that the y-axis is logarithmic scale for the nano-patterned Si data (up to the break point) and linear scale for planar Si. The legend in (g-j) demonstrate average SiNP's height.
• Figure 8 illustrates a schematic of steps involved in nano-patterning with BCPs, according to one embodiment.
• Figure 9 shows the AFM topography image of PS-£>-P2VP films solvo/thermal annealing at 70 °C, exposed to methanol, THF, toluene, toluene and methanol combined and THF and chloroform combined.
• Figure 10 shows the annealing time variation from 2 to 24 hours after exposure to THF:CHCl3 with volume fraction of (2:1 ) at room temperature.
• Figure 1 1 illustrates PS-£>-P2VP with different film thicknesses on Si substrate after exposure to THF and ChC at room temperature for 60 minutes. All images are 2x2 micron.
• Figure 12 (a) AFM topography image of PS-b-P2VP on GaN after phase separation and (b) top-down SEM image of GaN dots after pattern transfer.
• Figure 13 illustrates AFM topography image of the PS-b-P2VP films (a-d) after exposure to ethanol at 40 °C for 45 minutes and (e-h) after immersing the samples in ethanol at 40 °C for 45 minutes.
• Figure 14 illustrates the effect of critical film thickness and swelling ratio.
• the best ordered patterns are marked by purple frame or border.
• the films are exposed to THF:ChCI3 with different ratio.
• Figure 15 Iron oxide dots on (a) Si substrate and (b) GaN (LED) substrate after UV/Ozone.
• Figure 16 illustrates cross section SEM images of highly tuneable Si nanopillars made by large BCPs with relevant heights at (a) 180 nm, (b) 310 nm, (c) 515 nm, (d) 610 nm, (e) 870 nm and (f) 1 150 nm.
• the scale bars are 200 nm.
• Figure 17 illustrates SEM cross-section images of germanium nanopillars after 5- 30 minutes etch with relevant height of the nanopillars at (a) 370 nm, (b) 705 nm, (c) 800 nm, (d) 1080 nm, 1325 nm and (f)1370 nm.
• Figure 18 illustrates (a) AFM image of Ps-b-P2VP on glass, (b) Top-down SEM image of glass nanodots after pattern transfer of the metalised mask in (a), (b) SEM cross section image glass of nanopillars with metal oxide on top.
• the invention provides a solution based process based on high molecular weight block copolymer (BCP) nanolithography for fabrication of periodic structures on large areas of optical surfaces.
• BCP block copolymer
• Block copolymer self- assembly technique is a solution based process that offers an alternative route to produce highly ordered photonic crystal structures.
• BCPs forms nanodomains (5-10 nm) due to microphase separation of incompatible constitute blocks.
• the size and shape of the nanostructure can be customised by the molecular weight and volume fraction of the polymer blocks.
• the major challenge is BCPs do not phase separate into their signature ordered pattern above 100 nm, whereas for nano-features to be used as photonic gratings, they must be greater than 100 nm (typically 1 ⁇ 4 wavelength). This is due to significant kinetic penalty arising from higher entanglement in high molecular weight polymers.
• the invention produces block copolymers to phase separate into periodic domains greater than 100 nm.
• the process does not include any blending with homopolymers, or adding colloidal particles, disclosed in the prior art.
• a BCP mask is pattern transferred to silicon substrate by reactive ion etch (ICP-RIE).
• the final product can be black silicon, and consists of hexagonally packed conic Si nano-features with diameter above 100nm and periodicity of 200 nm. The height of the Si nanopillars varies from 100 nm to 1 micron.
• the antireflective properties of the Si nanostructures were probed in the 400 nm - 2500 nm wavelength range and compared to an Au reflectance standard.
• the subwavelength grating is made from the same material as the substrate (Si)
• the index matching at the substrate interfaces has led to highly improved anti-reflecting performance.
• the reflectivity of the silicon substrate shows one order of magnitude reduction in a broad range of wavelength from NIR to UV-visible, below 1 %.
• the invention provides a practical and effective way of fabricating high aspect ratio sub-wavelength structures (>100 nm to interact with light) on semiconducting substrates by using high molecular weight block copolymers (BCPs).
• BCPs high molecular weight block copolymers
• the samples yield structural superhydrophobicity for self-cleaning and structural colouring with no coating layer or pigmentation (antireflective coating), suitable for harsh environmental condition with high robustness and stability.
• Block copolymers do not phase separate above approximately 100 nm feature size due to high energy barrier involved with mobilising the highly entangles chain.
• the invention induces phase separation in hexagonally packed cylindrical forming BCPs with very high molecular weight (-800,000 g/mol) with no blending and no mixing with homopolymers.
• the photonic structure is kinetically trapped under extreme confinement regime and by finding the critical thickness range and swelling rate of the film during annealing.
• the pattern is successfully transferred to a semiconducting substrate. The result is an antireflective coating/ black Si with minimum reflectivity in a wide range of wavelength.
• Figure 1 illustrates large block copolymer PS-b-P2VP phase separated to hexagonally ordered pattern structure, (a) AFM topography image, (b) Fast Fourier Transform showing a very high level of order.
• the table provide the information regarding to the dimension of the features in (a).
• Figure 2 illustrates quantitative analysis of the feature size in Figure 1
• Figure 3 illustrates domain Size distribution of the sample in Figure 1 . 80% of the domains have feature size of 115 ⁇ 19nm.
• Figure 4 illustrates the pitch size distribution is 160-200 nm for 80% of the spacing in Figure 1
• Figure 5 illustrates SEM images of Si nanopillars fabricated by large molecular weight block copolymers. Top row, top down images with different etch time. Bottom row, the cross section image of the pillars with different height (d) 100 nm, (e) 485 nm and (f) 600 nm.
• surface texturing is employed. Roughening of the surface reduces reflection by increasing the chances of reflected light bouncing back onto the surface, rather than out to the surrounding air.
• a well ordered packed arrays of Si nanopillars are etched to a semiconductor substrate with heights varied from 100 nm- 1350 nm.
• BCPs are a way to pattern or texture the substrate which is a controlled process and a different process to roughening.
• the reflectance of Si decreases dramatically (>90%) in comparison to flat Si by changing the height of the pillars.
• the reflectance reduces progressively by increasing the pillars height from 100 nm to 600 nm and above.
• the 870 nanopillars show the best antireflective property.
• An added advantage is that the textured surface has the super-hydrophobic property in a way that repels water on a flat surface.
• Figure 6 illustrates optical characterisations of Si samples.
• Figure 7 illustrates, angular dependence of SiNPs with various height at different angle of incidence: (g) 45°, (h) 60°, (i) 70° and (j) 75°.
• the y- axis is logarithmic scale for the nano-patterned Si data (up to the break point) and linear scale for planar Si.
• the legend in (g-j) demonstrate average SiNP's height.
• the LED performance is improved by minimising the total internal reflection by nano-patterning the surface. Attempts have been made to prevent reflection by creating a refractive index gradient by providing nanometer level irregularities on the surface of light-emitting elements as well as extracting primary diffracted light by creating a diffraction grating on the surface.
• the approach of the present invention is more cost effective than other lithographic techniques and less harsh than chemical surface roughening currently used to enhance the overall efficiency of LEDs.
• chemical roughening process the uniformity and the depth of the grating cannot be controlled.
• BCP technique it is possible to fabricate high aspect ratio and ordered nano-features which improves the directionality of the beam where a more collimated beam profile is needed. These combined results cannot be achieved by surface roughening, as the light is scattered in different directions.
• the main problem is the cost and complexity of material processing. This include the expensive high temperature chemical vapour deposition of silicon nitride layer to make anti reflective coatings.
• the technology completely eliminates this step and therefore, it is a much simpler way of manufacturing black silicon for applications in highly efficient photovoltaics.
• the process is also environmentally friendly as it doesn't require the use of volatile and toxic silane or in fact any other harmful substances. This is a step towards green and clean energy resources.
• the black silicon produced according to the invention, can be used to enhance the sensitivity of image sensors in near infrared (NIR) regions for example in night vision cameras (for defence industry), medical imaging devices used in radiology, dental and dermatology. In telecommunication industry it can be used for taking a sharper image on mobile phone cameras.
• NIR near infrared
• Non-planar optical elements that can be treated according to the invention include optical lenses, metal microlens moulds, fiber optic lenses, etc.
• Planar optical elements that can be treated according to the invention include laser windows, optical polarisers, splitters and any other optical elements.
• FIG. 8 illustrates a process flow diagram for fabrication of sub-wavelength structures on the surface of LED substrates.
• the substrate material can be Silicon and a block copolymer (BCP) material is deposited on the substrate material.
• the block copolymer can be used as a sacrificial layer, metal oxide inclusion as hard mask and dry etch technique can be used to nano-pattern the surface to improve the efficiency of LEDs.
• the block copolymer is made of two or more chemically incompatible constitutes. The volume fraction of the constitutes can vary for example from 20:80 to 80:20. A higher molecular weight block copolymer (BCP) can be used to obtain long- range microdomains on the LED substrates.
• Figure 8 illustrates step by step process flow diagram of the fabrication of sub- wavelength structures on the surface of LED substrates, according to an exemplary embodiment of the invention.
• the polymer film is deposited from a solution comprised of one or two organic solvents.
• the solution can be used at room temperature or heated above a certain temperature.
• toluene:tetrahydrofuran with the ratio of 80:20 was used.
• the film can be deposited via spin coating, dip coating, spray or other methods of coating.
• step (ii) the polymer film is exposed to one or two organic solvent with a ratio that facilitate the chain mobilisation and lead to phase separation, either at temperature range RT to 200 °C and higher.
• THF: CHCb with volume ratio of 2:1 was used, for an hour at room temperature.
• Solvent annealing was carried out with two small vials containing 2 ml THF and 1 ml CHC placed inside a glass jar with a suitable volume, along with the BCP sample.
• step (iii) Phase separated BCP thin film were reconstructed by exposing the film to ethanol vapour. A 0.8 wt. % of iron nitrate ethanolic solution was spin cast on silicon substrate.
• Step (IV) UV/Ozone treatment was utilised to oxidize the precursor and remove the matrix polymer.
• the pattern is transferred to the substrate via an etch process.
• the silicon etch was performed using C 4 Fs (90 seem) and SFe (30 seem) gases for various duration of time with an inductively coupled plasma (ICP) and reactive ion etching (RIE) powers of 600 W and 15 W, respectively, at 2.0 Pa with a helium backside cooling pressure of 1 .3 kPa to transfer the patterns into the underlying substrate.
• the GaN etch was performed using CH 4 (5 seem), H2 (15 seem) and Ar (25 seem) gases for desired time with ICP and RIE powers of 500W and 45W.
• step (VI) the iron oxide is removed by immersing the samples in a diluted solution of oxalic acid bath. Solvent annealing of block copolymer films on silicon were performed.
• Figure 9 shows the AFM topography image of PS-£>-P2VP films solvo/thermal annealing at 70 °C, exposed to methanol, THF, toluene, toluene and methanol combined and THF and chloroform combined. All images are 2x2 micron. From figure 9 it is clear that combination of THF and chloroform (Fig. 9y-z3) at 70 °C, induces the best phase separation with highest level or order among others. After 30 minutes the phase separation starts (Fig 9.y) and after 2 hours annealing a well ordered pattern is forms (Fig. 9 z3). Clearly the combination of tetrahydrofuran and chloroform provides the best morphology.
• the annealing time is varied from 2 hours to 24 hours, at room temperature.
• the critical thickness is examined.
• the film is annealed for 1 hour only at room temperature with (THFiChCb).
• the film thickness varied between 25 to 356 nm in this example.
• the PS-b-P2VP thin film was formed by spin coating the block copolymer solution (4500 rpm for 30 s).
• FIG. 10 shows the annealing time variation from 2 to 24 hours after exposure to THF: CHCb with volume fraction of (2:1 ) at room temperature. Further tuning of the thickness led to reduction of annealing time to an hour at room temperature, exposed to (2:1 ) (THFiCHCb) in a confined and specified volume jar. The best result is achieved when a critical thickness is obtained, as illustrated in Figure 10.
• the diameter of features at figure 10 was measured -1 15 nm using AFM topography images. The images are 2x2 micron.
• FIG. 12 (a) polymer film phase separated on LED substrate, 12(b) after pattern transfer (GaN)). GaN was used as LED substrate and PS-k-P2VP BCP was spin coated and annealed with THF and chloroform (2:1 ) as annealing solvents at room temperature for 60 minutes. Phase separated BCP thin film were characterized using AFM and microdomains were ⁇ 1 10 nm in diameter.
• FIG. 13 illustrates AFM topography image of the PS-b-P2VP films (a-d) after exposure to ethanol at 40 °C for 45 minutes and (e-h) after immersing the samples in ethanol at 40 °C for 45 minutes.
• the images are 2x2 microns.
• the film didn't survive the process. The structure was not retained and the films were delaminated from the substrate. To solve this problem, the films were exposed to ethanol vapour at 40 °C.
• FIG. 13b The result is shown in figure 13 (a-d). After 30 minutes exposure a controlled pattern is reconstructed (Fig. 13b). To deposit the iron oxide in P4VP domains, 0.8% weight percent of iron (III) nitrate nonahydrate (Fe(N03)3. 9H2O) in ethanol solutions were spin-coated onto the activated film. UV/Ozone treatment was used to oxidize the precursor and remove the polymer. These iron oxide nanodot arrays were used as a hard mask for pattern transfer onto the substrate.
• Figure 14 illustrates the effect of critical film thickness and swelling ratio.
• the best ordered patterns are marked by frame or border.
• the films can be exposed to THF:ChCl3 with different ratio, where the ratio can be from 1 :1 to 10:1 or other way round depending on the application.
• Iron nitrate solution was spin coated after ethanol treatment and exposed the film to UV/Ozone for 120 min to oxidize the precursor and to remove the polymer.
• Figure 15 shows the AFM topography image of the iron oxide on silicon and GaN LED substrate. Fabricated iron oxide dots are -1 10 nm in diameter. Sub-wavelength structures on substrate were fabricated by pattern transferring iron oxide dots to the substrate using a dry etcher.
• the height of the structures can be precisely controlled by increasing the silicon etch time.
• Figure 16 illustrates cross section SEM images of (a) 180 nm high Si nanopillars after 5 minutes Si etch, (b) 310 nm high Si nanopillars after 10 minutes Si etch, (c) 515 nm Si nanopillars after 20 minutes etch, (d) 610 nm Si nanopillars after 30 minutes etch, (e) 870 nm Si nanopillars after 40 minutes etch, (f) 1 150 nm Si nanopillars after 50 minutes etch.
• the diameter of the base is 76-136 nm.
• the apex diameter is varied 75-91 nm.
• Figure 17 illustrates SEM cross-section images of germanium nanopillars after 5- 30 minutes etch with relevant height of the nanopillars at (a) 370 nm, (b) 705 nm, (c) 800 nm, (d) 1080 nm, 1325 nm and (f)1370 nm.
• Figure 18 illustrates(A) AFM image of Ps-£>-P2VP on glass, (b) Top-down SEM image of glass nanodots after pattern transfer of the metalised mask in (a), (b) SEM cross section image glass of nanopillars with metal oxide on top.
• -Optical devices and applications such as high-power laser windows, mobile phone screen covers, microlens arrays.

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• 2016
  • 2016-01-14 GB GBGB1600745.2A patent/GB201600745D0/en not_active Ceased
• 2017
  • 2017-01-13 CN CN201780016794.2A patent/CN108886064A/zh active Pending
  • 2017-01-13 WO PCT/EP2017/050736 patent/WO2017121888A1/en active Application Filing
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• 2022
  • 2022-01-12 US US17/573,994 patent/US20220365248A1/en not_active Abandoned

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